How much power has Congress given the president? On Friday, defending Mr. Trump’s executive order in a Seattle courtroom, Michelle Bennett, a Justice Departmen

How much power has Congress given the president? On Friday, defending Mr. Trump’s executive order in a Seattle courtroom, Michelle Bennett, a Justice Department lawyer, cited Youngstown Sheet & Tube Co. v. Sawyer, a 1952 decision in which the Supreme Court rejected President Harry S. Truman’s assertion that he had the authority to seize steel mills during the Korean War. The most famous part of the decision is a concurrence from Justice Robert H. Jackson, which set out a framework for considering clashes between presidential power and congressional authority. The president has the most power when he acts with congressional authorization, Justice Jackson said, and an intermediate amount when Congress is silent. The president’s power is at its “lowest ebb,” Justice Jackson wrote, when Congress has forbidden a particular action. Truman’s actions fell into the third category, Justice Jackson wrote. Ms. Bennett, by contrast, said Mr. Trump’s order was in the first category. “Here we have the president acting pursuant to power that Congress gave him, which means, under the Youngstown steel seizure case, he’s acting at the apex of his power,” she said. A key part of immigration law does give the president broad power. It says, “Whenever the president finds that the entry of any aliens or of any class of aliens into the United States would be detrimental to the interests of the United States, he may by proclamation, and for such period as he shall deem necessary, suspend the entry of all aliens or any class of aliens as immigrants or nonimmigrants, or impose on the entry of aliens any restrictions he may deem to be appropriate.” But another part of the law forbids discrimination “because of the person’s race, sex, nationality, place of birth or place of residence,” but only “in the issuance of an immigrant visa.” The Trump administration argues that the power to bar entry, the subject of the first law, is broader than the limits on issuing visas. What about arguments based on religious discrimination? Lawyers for Washington State have said that the executive order violates the First Amendment’s prohibition against government establishment of religion because its provisions on the refugee program favor minority religions. “President Trump and his advisers have made clear that the very purpose of this order is to tilt the scales in favor of Christian refugees at the expense of Muslims,” they wrote in their brief to Judge Robart. The Trump administration urged the Ninth Circuit to reject arguments based on religious discrimination, even though Mr. Trump has said he meant to favor Christian refugees. Judicial consideration of the president’s motives, the brief said, would violate the separation of powers. “The more searching inquiry envisioned by the states would create substantial separation-of-powers problems, by permitting probing of the president’s subjective motive in issuing the order,” the brief said. Could the case founder on the issue of injury? The states challenging the order face the initial hurdle of demonstrating that they have suffered the sort of direct and concrete harm that gives them standing to sue. Judge Robart ruled that they did, relying on a decision from the federal appeals court in New Orleans, which said Texas could sue to challenge President Barack Obama’s plan to defer the deportation of millions of unauthorized immigrants and allow them to work. “The executive order adversely affects the states’ residents in areas of employment, education, business, family relations and freedom to travel,” Judge Robart wrote. He said the states had been hurt because the order affected their public universities and their tax bases. In its Ninth Circuit brief, the Trump administration called the states’ asserted injuries “attenuated and speculative” and did not address the Texas decision. In court in Seattle on Friday, Ms. Bennett said the government disagreed with the Texas ruling. Follow Adam Liptak on Twitter @adamliptak. A version of this article appears in print on February 6, 2017, on Page A11 of the New York edition with the headline: The President Has Much Power Over Immigration, but How Much?. Order Reprints| Today's Paper|Subscribe Continue reading the main story Related Coverage Trump Clashes Early With Courts, Portending Years of Legal Battles FEB. 5, 2017 Lifting of Travel Ban Sets Off Rush to Reach U.S. FEB. 5, 2017 Where Trump’s Travel Ban Stands FEB. 5, 2017 Trump Protesters Borrow From Tea Party to Put Pressure on Lawmakers FEB. 5, 2017